Peanuts (Arachis hypogaea), hens' eggs, and milk are well-known three common allergens in the United States. Among them, peanuts (especially their seeds) cause serious allergy symptoms including anaphylactic shock, which may be fatal. Besides, peanuts have other problems in that they can induce allergic responses even when they are present in a small amount, and that heat-treated peanuts exhibit enhanced allergenicity. On this account, it is very important to check the presence of peanuts as a raw material in processed foods, manufacturing lines thereof, etc.
Allergens, which are substances causing allergies, generally are proteins and degradation products thereof (peptides), and the mainstream approach for analyzing the allergens is to use antibodies against the allergens as antigens. As for peanuts, there has been reported a method for detecting peanut allergens using an antibody against an Ara h1 protein, which is a major allergen in peanut seeds, for example (Patent Document 1).
However, it is difficult to provide a simple and low-cost test method using an antibody because the antibody, which is a protein, has a problem in stability. On this account, in recent years, a nucleic acid molecule that specifically binds to an antigen is attracting attention as a substitute for an antibody. However, no nucleic acid molecule that binds to peanut allergens has been reported heretofore. Furthermore, even a small amount of peanuts can be harmful as described above. Thus, there is a demand for improvement in specificity and accuracy of analysis.